1. Field of the Invention
This invention relates to a servo control circuit module or unit designed for use in a television camera, and more particularly to a composite servo control circuit module comprising a speed-servo control circuit and a position-servo control circuit which is responsive to exterior signals for automatically selecting either the speed-servo control circuit or the position-servo control circuit.
2. Description of the Prior Art
There has been hitherto known a television camera system detachably equipped with servo control modules for focussing and zooming of an associated zoom lens. These focussing and zooming servo control modules are designed to be used in common or interchanged with each other. When the servo control modules are detacted from the television camera, focussing or zooming control can be effected manually.
The adaptability of one of these different servo control modules to the other (that is, their interchangeability) is a great advantage both in production and operation.
Generally, a position servo control circuit is used to effect focussing control, whereas a speed servo control circuit is used to effect zooming control. In an attempt to make those different servo control circuits interchangeable with each other in use, a servo control module may be designed which consists of those parts and circuits which the position- and speed-servo control circuits have in common, and an associated lens system may be designed as containing those remaining parts and circuits (which belong exclusively to the position- and speed-servo control circuits) in the focussing and zooming sections of the lens system respectively.
Recently there has been a demand for effecting, in addition to position servo control, speed servo control in focussing, and for effecting, in addition to speed servo control, position servo control in zooming. Also, conventional position- and speed-servo control circuits have a small number of parts in common with each other. Accordingly, an interchangeable module has such a small number of common parts built therein that a large number of remaining exclusive parts and connections must be provided to the television lens system. This devalues the merit both in design and production attributable to their interchangeability. Processing of different electric signals and mechanical coupling become increasingly difficult, too.